1. Field of the Invention
The present invention relates to a vertical semiconductor device used for high power switching and having good withstand voltage characteristics, and a method for producing the semiconductor device.
2. Description of the Related Art
High reverse breakdown voltage and low on-resistance are required for high current switching elements. Field effect transistors (FETs) that use a group III nitride semiconductor are superior in terms of high breakdown voltage and high-temperature operation because of their large band gap. In particular, vertical transistors that use a GaN-based semiconductor have been receiving attention as transistors for controlling high power. For example, there has been proposed a vertical GaN-based FET whose mobility is increased and whose on-resistance is decreased by forming an opening in a GaN-based semiconductor and forming a regrown layer including a channel of two-dimensional electron gas (2DEG) on the side surface of the opening (refer to Japanese Unexamined Patent Application Publication No. 2006-286942).